Musnad Ahmad 121:1

Ya'qub narrated to us, my father narrated to us, from Ibn Ishaq, who said: Muhammad ibn Ibrahim ibn al-Harith al-Taymi narrated to me, from Abu al-Haytham ibn Nasr ibn Dahr al-Aslami, from his father, who said: Ma'iz ibn Khalid ibn Malik—a man from among us—came to the Messenger of Allah, peace and blessings of Allah be upon him, and confessed against himself to adultery. The Messenger of Allah, peace and blessings of Allah be upon him, ordered us to stone him. We went out to the Harrah of Banu Nayyar and stoned him. When he felt the touch of the stones, he became extremely distressed. When we finished with him and returned to the Messenger of Allah, peace and blessings of Allah be upon him, we mentioned his distress to him. He said: "Why did you not leave him?"